I have just found out my father is having double heart...

I have just found out my father is having double heart bypass surgery. Fourteen years ago, he was in an accident which damaged his back to such an extent that he was registered disabled and was told to use a wheelchair. He's quite stubborn and he still walks with the aid of a crutch. He had keyhole surgery on his back to help relieve some of the pain but he is still on a lot of different pills a day for the pain/blood pressure/side effects of the pain medication. Because he can't move around a lot, he became overweight and developed diabetes. I need to know if his previous condition will have an effect on this operation. Will the fact that he was on so much medication (all prescribed by our doctor) put him in any danger? Thank you in advance.